adding a sim plug to a tx

[olmod]

I have a number of older tx's is it possible to add a sim connector to them?
thanks in advance , cheers :)

[slipstick]

It's often possible if you have access to an oscilloscope to find the appropriate signals inside them. Depends what they are though e.g. the signal on very old Futuba Txs uses a different centre value from all modern Txs so won't work with most sims.

Steve

[andrew b]

you will usually find a suitable signal across the xtal socket on older FM futaba transmitters :)

[olmod]

Thanks guys ,the radio i had in mind is a JR max 5 (36mhz) wich is in very nice condition. cheers . :) btw Andrew I love diesels too :) the only one i have left now is a mills .75.

[andrew b]

Thanks for the diesel support :) I would say that the greatest percentage of older FM transmitters use the same system to achieve FM, that is to apply the modulation voltage across a varicap diode that is in parallel with the Xtal, thereby producing an FM signal. cheap and cheerful way to do it :eek:

[olmod]

Its sounds as tho' this may be a nice winter project :) its "orrible" weather here in Melbourne at the this time of year :( I will have to sort out some sort of circuit and get a sim so i can at least get in a bit of practice :) im getting rusty :D

[andrew b]

Hi again Mr Olmod, I found this diagram in another forum. The FM modulator part is at the bottom left of the circuit, centered around the varicap diode/Xtal

[olmod]

Thanks Andrew ,i will get a EE buddy to have a look ,its not clear to me what connections / mods' even what socket would be needed :o but someone certainly put a bit of time into hand drawing and tracing out that circuit and i can appreciate the effort. cheers, LEZ . :)

[bindibadgi]

Hey, this might be what I'm after too. Am I reading this right that it's possible to make a plug which would replace the Xtal and create a PC link from there?

Go easy; I am a newbie! ;)

[andrew b]

The only thing I am saying is that "The modulation voltage/pulse signal exist on one pin of the Xtal" how you use it is up to you, just dont short it to ground